Fluid operated braking system for aircraft



May 29, 1951 H. J. BUTLER FLUID OPERATED BRAKING SYSTEM FoR AIRCRAFT 2 Sheets-Sheet l Filed Dec. 4, 1948 Filed Dec. 4, 1948 May 29, 1951 H. J. BUTLER 2,555,184

FLUID OPERATED BRAKING' SYSTEM FOR AIRCRAFT 2 Sheets-Sheet 2 INVENTOR. HENRY JAMES BUTLER HIS HTTORNEY UNITED STATES PATENT OFFICE FLUID OPERATED BRAKING SYSTEM AFOR AIRCRAFT Henry James Butler, Sutton Coldield, England,

assigner to Dunlop Rubber Company Limited, London County, England,.a Brtish'company Application December 4, 1948, Serial No. 63,559 In Great Britain December 18, 1947 This invention relates to an improved fluid operated braking system foraircraft.

Aircraft brakes are usually operated from a source of fluid pressure which can be applied to the brakes when required through a valve which is under the control of the pilot.

In this system the braking pressure employed depends solely on the judgement of the pilot. If the pressure should be too little he can gradually increase it but if on landing he should apply too great a pressure, the tyres may become damaged through the locking of the wheels and a serious accident result. There is indeed a maximum pressure that should not be exceeded when it is desired to brake the aircraft in the shortest distance without damage to the tyres. This pressure is not constant but varies with the load on the aircraft, being greater as the load is increased.

It has been proposed to provide means actuated by the load on the aircraft wheels for automatically supplying pressure fluid to the wheel brakes and so operating themwhen the aircraft touches down. Such means, however, is purely automatic and the braking pressure applied is pre-determined in relation to the load on the wheel and cannot be modified by the pilot. However, though it is desirable to prevent a pilot from applying a braking pressure exceeding a maximum, which varies with the load on the wheel, it is also desirable that he should be able to reduce the pressure below this maximum if necessary.

It is the object of the present invention to provide a fluid pressure operated braking system for aircraft comprising means actuated by the load on the wheels for automatically supplying pressure fluid to the brakes wherein the braking pressure so produced can be varied by the pilot up to a pre-determined maximum.

According to the present invention a fluid pressure operated braking system for aircraft in Which the wheels are mounted on oleo struts provided with means whereby increase of internal pressure in the legs provides a source of pressure for the automatic and independent application of the brakes comprises means for relieving the said internal pressure by the application of pressure from an independent source of uid pressure.

According to the preferred construction an aircraft braking system comprises an oleo leg comprising a strut portion, a sleeve enclosing the extremity of the said strut portion having a stub axle adapted to carry a wheel, the said 4 Claims. (Cl. 244-111) strut portion and sleeve being so formed as to provide a base space between the base of the strut portionand the base of the sleeve and an annular space between the sides of the strut portion and the sides of the sleeve, a pipe connection from one space to a fluid-operated brake mechanism on the said wheel, and a pipe connection between the other space and a source of ui'd pressure supply under the control of the pilot. v

The invention will now be more particularly described with reference to a braking system in which the two bodies of fluid are disposed in cavities formed between the base of an aircraft leg of circular cross-section and an enclosing sleeve integral with a stub axle on which the wheel is rotatably mounted. A suitable link Figure 1 shows in diagrammatic form a crosssection of base of an aircraft leg, and

Figures 2 and 3 show respectively diagrammatic views in elevation and plan of the link connection between the leg and the sleeve.

Fig. 4 is a diagrammatic sketch of a braking system incorporating the aircraft leg of the present invention.

Referring to the drawings, the device comprises an aircraft leg 1 slidably carried in an enclosing sleeve 8. The internal diameter of the lower end 4 of the sleeve is smaller than that of the main portion thereof and a similar reduced diameter Yportion 3 is formed on the lower end of the leg and is a sliding fit in the reduced diameter portion of the sleeve. Sealing rings 9 are provided in the reduced diameter portion of the leg and at the base of its larger diameter portion to seal the cylinder and annular chambers formed respectively by the reduced diameter portions of the leg and sleeve and by the radial and axial faces of the sleeve and leg at the junctions of the reduced and larger diameter portions thereof. The cylindrical chamber l contains a hydraulic fluid and has a pipe connection I0 with fluid-operated brake mechanism While theannular chamber 2 contains hydraulicfluid and has a pipe connection I4 with a source of fluid pressure under the control of the pilot.

Fig. 4 shows the system diagrammatically. The source of iiuid pressure is either an accumulator I I' or a pump, compressor or the like which delivers pressure fluid through the line I2, to a diierential control unit I3 under the control of a pilot which in turn transmits pressure uid along the lines I4 to the two annular chambers 2 each adjacent the bottom of an aircraft leg 1. The cylindricalchamber I atfthe bottomfofeach leg communicates, `through the'line I0 with .a brake associated with a wheel I9 secured to the bottom of the leg.

The link connection illustrated on Figures 2 and 3 is denoted by the reference r"6 in Figure 1 while the reference 5 indicates a stub axle integral with the sleeve 8.

The operation of the system is .as rfollows. When the aircraft is parked'thefbrakeseare applied by releasing the fluid ,pressure in the annular chamber so that the 'whole :weight ofthe aircraft is carried by the fluid inthe 'cylindrical chamber and is transmitted to the brakemechanism. When the pilot prepares to take-off the .annular chamber is placed in .communication .withthesource of .fluid pressureand thepres- .sure .in .the said chamber is thereby increased, which .causes the leg to .move axially upward and relieve the,pressure.in.the cylindrical chamber,.thus releasing. the brakes.

`On ,preparing to .land '.the pilot.can-partiall.y `or .wholly .release the .duid v.pressure .in .the annular chamber but in any. case .the .braking pressure applied will never exceed that due to .the .load on` the wheels.

The construction .is equally `applicable .to .twin .wheels .if .a .stub .axle is provided .on each .side ofthe sleeve.

.Having .described .my .invention -what I yclaim .ist

.1. Affiuid pressure .operatedaircraft braking .system which comprises ran oleo legcomprising -a strut portion, .a sleeveenclosing .the ,extremity of the said strut portion .having .a .stub axle adapted to .carry a vwhee1,.the.said strut .portion .andsleeve beinglsoformed .as vto provde'abase space betweenlthebaseof thestrut portion-.and the base .of the .sleeve .and an annular .space between the sides of the strut portion and the sides of the sleeve, a pipe connection from one space to a fluid-operated brake mechanism on the said wheel, and a pipe connection between the other space and an independent source of .iiuid pressure. supply.

2. A fluid pressure'operated aircraft braking system which comprises a strut, a wheel carrying .member slidable in an axial direction relative to said strut, an expansible fluid supply chamlber having an foutlet for connection to said braking system and compressed by pressure of said .strut on-said .wheel carrying member to imparta proportionate pressure to fluid in said :.chamber,fand.anzexpansible control chamber between said strut and said wheel carrying member tand having =an inlet for pressure uid to 'oppose'and control the pressure of said strut on saidwheel carrying member.

3. The apparatus of claim 2 in which said ...suppl-y .chamber .and said .control l chamber Yeach comprises'a cylinderand a pistonslidableinsaid cylinder.

4. The apparatus .of .claim 2 in which .said

125 .supply chamber comprises a cylinder in .said

wheel carrying vlmember slidably tting a `por- -.tion of said .strut .and in which .said .control chamber comprisesa cylinder in said .wheel carrying .member-co-axial with that of .said suppl-y chamber and slidably tting said strut.

HENRY `JAMES BUTLER.

EREFERENCES CITED The following .references vare of record in'the file of this patent:

UNITED STATES PATENTS 

